This invention relates to a switching arrangement operable by a tone of a predetermined frequency and in particular to a loop-back unit utilizing such a switching arrangement.
Various establishments, for example banks, department stores, etc., use computers and sometimes transmit and receive data over communication lines, for example, telephone lines. If problems develop in the transmission and/or receiption of data over the telephone lines, it becomes necessary to determine whether the problem exists in the telephone lines (or related equipment) or in the customer's equipment, that is, his computer or equipment interfacing the computer with the telephone lines. For this reason, it is desirable for the telephone company to be able to determine easily whether or not the problem exists in their equipment or in the customer's equipment and it is preferable if this can be determined without having to send a service man to the customer's premises, i.e. if it can be done remotely. The present invention enables this to be done by setting up a connection at the customer's premises such that signals can be sent and received to and from the customer's premises without going through his equipment, i.e. his computer or other data equipment. This is called "looping back" and, according to the invention, the looping back is initiated by a tone sent over the telephone line to a loop-back unit located at the customer's premises.